FIG. 1A is a diagram illustrating an update procedure of an uplink channel descriptor (UCD) according to the related art.
It is assumed that UL-MAP is transmitted per frame in a state that a frame duration period is 20 ms, and a UCD transmission interval is 10 s. Also, a mobile station has already received UCD of which configuration change count is “i”. A base station transmits UL-MAP, of which a UCD count is “i,” per 20 ms (S101, S102). The base station retransmits the UCD message, of which the configuration change count is “i,” at the time when the UCD message will be transmitted (S103). The mobile station which has received the UCD message decodes the corresponding message and then compares a configuration change count included in its own UCD with the configuration change count of the newly received UCD. If the configuration change counts are identical with each other, the mobile station ignores system information included in the newly received message (S104). The base station continues to transmit UL-MAP, of which the UCD count is “i,” per 20 ms (S105). If the system information has been changed (S106), the base station transmits a configuration change count “i+1” and the changed UCD message at a corresponding transmission time (S107). The mobile station decodes the corresponding message and then compares the configuration change count included in its own UCD with that of the newly received UCD. If the configuration change counts are different from each other, the mobile station stores the system information of the newly received message (S108). The base station continues to transmit UL-MAP, of which the UCD count is “i,” per 20 ms (S109, S110). The base station retransmits the previously transmitted UCD message at the corresponding transmission time and starts a UCD transition interval timer (S111). If the timer expires, the base station transmits UL-MAP of which a UCD count is “i+1” (S112). The mobile station which has received the UL-MAP deletes the existing UCD system information and applies new UCD system information (S113). The above steps are similarly performed for a downlink channel descriptor (DCD) message.
As described above, the base station transmits system information per long interval as one message. In this case, the mobile stations decode the message every time to identify whether system information has been updated, and may store and update system information which does not need to update. Also, for application of the changed system information, the mobile station may need much time.
FIG. 1B is a diagram illustrating relations of a super-frame, a frame, a subframe, and OFDM symbols of the IEEE 802.16m system.
In an example of FIG. 1B, one super-frame has a length of 20 ms, and four frames each having a length of 5 ms are provided. A super-frame header exists at the starting position of the super-frame. The super-frame header includes super-frame header system information and broadcasting messages. The super-frame header can include a structure of several symbols, or several subframes. One frame of 5 ms includes eight subframes, each having six OFDMA symbols.
FIG. 2 is a diagram illustrating scheduling of system information of each of a legacy mobile station and a new mobile station.
In this case, an optimized system information transmission mode can be used to fulfill requirements (for example, TGm SRD-IEEE 802.16m-07/002r4) of a new system. However, since system information is transmitted through both a legacy zone and a new zone, a waste of radio resources may be caused.
It is to be understood that the technical problems to be achieved by the present invention are not limited to the aforementioned technical problems, and any other technical problems which are not described will be apparent from the detailed description of the present invention to those skilled in the art to which the present invention pertains.